The present invention relates to an optical fiber assembly, an optical module including an optical fiber assembly, and a manufacturing process thereof.
With wide spreading use of optical telecommunication in human society, there is an increasing impetus to deploy optical subscriber systems including optical home terminals.
FIG. 1 shows the construction of a typical optical home terminal 10.
Referring to FIG. 1, the optical home terminal 10 includes a housing 11 in which a circuit assembly 12 is accommodated. The circuit assembly 12 includes a printed circuit board 13 carrying thereon various electronic components 14 and an optical fiber assembly 15. In order to reduce the cost of the optical home terminal 10, it is desired to mount the optical fiber assembly 15 and the electronic components 14 on the printed circuit board 13 by a solder reflowing process. Further, it is desired to reduce the cost of the optical fiber assembly as much as possible.
FIG. 2 shows the construction of a conventional optical fiber assembly 20.
Referring to FIG. 2, the optical fiber assembly 20 includes a housing 21 accommodating therein an optical device 22. The housing 21 includes a through-hole 25, and a ferrule 24 provided at an end of an optical fiber 23 is fitted into the through-hole 25. Further, a lens 26 is disposed between the foregoing end of the optical fiber 23 and the optical device 22 in the housing 21. Thereby, an optical fiber cable 27 extends outside the housing 21.
In operation, the optical beam emitted by the optical device 22 is injected into the optical fiber 23 after being focused by the lens 26. Further, the optical beam exited from the foregoing optical fiber end is focused upon the optical device 22 by way of the lens 26.
FIGS. 3A and 3B show another conventional optical fiber assembly 30.
Referring to FIGS. 3A and 3B, the optical fiber assembly 30 includes a housing 31 in which a block 32, a ferrule 33 and a split sleeve 34 are accommodated, wherein the block 32 includes a V-shaped groove 32a and a flat top surface 32b for carrying an optical device 35. The ferrule 33 holds therein an optical fiber 36 such that a free end part of a bare optical fiber extends from the ferrule 33. Thereby, the bare optical fiber 36 thus extending from the ferrule 33 is held by the V-shaped groove 32a such that the end of the optical fiber 36 faces the optical device 35 within an error of .+-.1 .mu.m. As noted already, the ferrule 33 is held by the split sleeve 34.
Further, a ferrule 37 of an optical connector is inserted into the housing 31 for a fitting engagement with the split sleeve 34.
In the construction of FIG. 2, there is a drawback in that the optical fiber assembly 20 cannot be mounted on a printed circuit board by a solder reflowing process because of the existence of the optical fiber cable 27 extending from the optical fiber assembly 20. Thus, it has been necessary to mount the optical fiber assembly 20 manually on the printed circuit board, while such a manual mounting process increases the cost of the optical home terminal. In addition, the optical fiber assembly 20, using the lens 26 therein, has a complex structure and the assembling process thereof is difficult. In other words, the construction of the optical fiber assembly 20 itself is disadvantageous for reducing the cost of the optical home terminal.
On the other hand, the optical fiber assembly 30 of FIGS. 3A and 3B, lacking the optical fiber cable extending therefrom in the outward direction, can be mounted on a printed circuit board successfully by using a solder reflowing process. On the other hand, the optical fiber assembly 30 has a drawback in the point that the bare optical fiber 36 having a diameter of only 125 .mu.m may be damaged when assembling the optical fiber assembly 30. Thus, the yield of the optical fiber assembly 30 is tend to be deteriorated and the cost of the optical home terminal is increased.
While it is possible to construct such that the ferrule 33 engages the V-shaped groove 32a, such a construction cannot provide the necessary accuracy of positioning the optical fiber in view of the fact that the ferrule 33 has a diameter of 1-2.5 mm and cannot be positioned precisely within the error of .+-.1 .mu.m by engaging with the V-shaped groove 32a. Further, it is difficult to form the V-shaped groove 32a with a size of 1 mm or more for accepting the ferrule 33 while still maintaining the foregoing precision of .+-.1 .mu.m.